In printed circuit technology, a printed circuit terminal card is employed which comprises an edge connector containing a plurality of electrical contacts which have their ends on one side of the connector fixed to electrical tabs arranged along one edge of the card. The ends of the contacts on the other side of the connector are pluggable sockets which are electrically plugged to another printed circuit card or board, or the like, which generally would be on the same machine.
On one surface of the printed circuit terminal card is a plurality of electrical terminals or tabs which are solder connected respectively to the ends of a plurality of wire conductors carried in a cable. This cable, for example, could be a power cable which is connected to a power supply. It may be connected internally to the same machine or it may be connected to remote peripheral equipment. It may be necessary from time to time to either repair or replace the terminal card or, as is more often the case, repair or replace the printed circuit card or board to which it is plugged. This necessitates the unplugging of the edge connector. Due to the density and complexity of the arrangement of components and wiring on present day electronic machines, the edge connector generally cannot be reached and so it has to be unplugged by pulling on the cable. This creates a problem in that a strain is placed on the individual wire conductors soldered to the card and breaking of the solder connections occurs.
Strain relief devices have been proposed and used before in an attempt to eliminate this problem. For example, in the case of a flat cable, a snap lock clamp bar has been proposed wherein the end portion of the cable is looped under the bar to allow strain on the cable to be taken up by coaction between the loop and the bar. However, this arrangement would not work satisfactorily for the present application where the end of the cable splits into a plurality of individual conductor wires which are soldered to the circuit board. In another type of strain relief device, a self-locking plug is inserted into a receptacle on a cable connector card clamping a strand of wires into the holes of the card to eliminate the strain at soldered terminals. This arrangement is adapted for use with a flat cable where the individual wires are of uniform size and are not bunched up. Other strain relief devices make use of clamping bars or plates which are clamped together by means of screws. This type of device proved to be time consuming and costly and resulted in poor control of the pressure on the wires. The use of screws can result in too much pressure being applied on the wires which causes the insulation to split or break open and shorts to occur. It became evident that a strain relief device was required which was economical, simple to assemble, and which could be easily used without uncontrolled pressure being applied to the wires.